Audio is an essential element in any modern-day religious service. What is heard by the congregation is a combination of the acoustic qualities of the room and the performance of the audio system.
Some of the desirable acoustic qualities in a house of worship are:
Reverberance: When well controlled with early decay, the effect is perceived as a beautiful sound that enhances the quality of the audio. See the Rane Pro Audio Reference for a definition of “reverberation.”
Clarity: The ratio of the energy in the early sound compared to that in the reverberant sound. Early sound is what is heard in the first 50 - 80 milliseconds after the arrival of the direct sound. It’s a measure of the degree to which the individual sounds stand apart from one another.
Articulation: Determined from the direct-to-total arriving sound energy ratio. When this ratio is small, the character of consonants is obscured resulting in a loss of understanding the spoken word.
Listener Envelopment: Results from the energy of the room coming from the sides of the listener. The effect is to draw the listener into the sound. Where a conference room would be optimized for articulation and clarity, a symphony hall is optimized for reverberance and listener envelopment. A good house of worship is optimized as a compromise between the somewhat conflicting requirements of music performance and the spoken word.
Articulation must be excellent but sufficient reverb is required to complement music performances. All reflections must be well controlled to achieve this balance and ensure the best possible listener experience.
An Example Of Good Sound
There are other possible examples, but the author really likes this one: In some mosques, cathedrals and tabernacles there are wonderful domed ceilings that have marvelous natural acoustic properties.
The acoustic coupling from performers to the congregation grouped under the dome makes for a very (dare I say) “spiritual” experience. For the purpose of this article, this level of performance is a “gold standard” to which other acoustic spaces will be compared in the search for improvements and recommendations.
The USA Pavilion at Florida’s Epcot Center makes for an interesting case study. There is a dome ceiling in the pavilion. Under the dome an eight-part acappella group called the “Voices of Liberty” performs. For those under the dome listening to the group, the sound is beautiful and inspiring. Moving out from under the dome, the “magic” is gone.
This level of performance is not feasible in a typical house of worship, but it does establish an icon as to what could be if there was sufficient skill (and budget) applied to the acoustic and audio system design.